Here's thought - instead of asking us about a relatively new plant, why not ask PuckerButt? Ed Currie developed the Carolina Reaper and founded the company. Their website has a lot of information on growing, from germination to harvest, with a section on light. (FYI, for artificial light he recommends T5 fluorescent.)
I grew a Carolina Reaper last year in our raised beds. It was an odd growing year here - things got going late. It grew to nearly 4 ft tall. The Leaves were a beautiful rich deep green - much darker than yours in the photos. It had hundreds of blooms, probably thousands in all, but only 1 or 2 set. Then towards the end of the season the started setting like crazy. Unfortunately only a handful got any size to them and only 2 ripened on the plant. So when the danger of frost was imminent, I picked them all, even the tiny 1/2 inch ones. I put them in a large brown bag and eventually every one of them ripened - all 200+ of them! I won't be growing Carolina Reapers again for a long time. I made sauce - more of a paste consistency - and a very very little goes a very very long way! The flavor is excellent, but it is extremely hot.
Interestingly, I also grew a Mad Hatter right next to it. The hottest and the mildest chilies right next to each other! It was prolific all season long!! I got hundreds of gorgeous ones. Again I had issues with them ripening, but the paper bag method worked great. They also have excellent flavor, either green or red, but virtually no heat (I call them the chili hater's chili) and are excellent thinly sliced in salads, on sandwiches, etc. They are very crisp and crunchy, even retaining their crunch after cooking. We even sprinkle them on charcuterie boards for parties and people love them. We will definitely be growing them again every year.
Incidentally, the reflectivity of aluminum foil is higher than paint over the entire spectrum - in addition to being a non organic finish, which is higher anyway. Organic finishes absorb more light - including in the UV (required for photosynthesis) and IR (heat) frequencies. There is not a huge difference in the reflectivity and absorption coefficients of different colors outside the visible range - except black, but that is due to the fact that virtually all black pigments are carbon which itself has slightly higher coefficients.
